Does anyone know what DB and table tells what sites users
belong to?

I was thining it was xxx_Sites.UserInfo however, if you
run a query against a particular site, then remove users
from that site, the users still show up in the UserInfo
table.

Basically I need to design a stored procedure that can
query what users belong to what sites, so I can run a
script that removes the users every night. So al I need
to know, is where this information is stored.